Internet Protocol (IP) Multimedia Subsystem (IMS) is an architectural framework for providing multimedia services across a variety of access platforms. IMS facilitates multimedia service creation and deployment based on Internet protocols allowing IMS subscribers to access personalized interactive, multimedia services, on any device, and anywhere. IMS is access-agnostic, whereby service delivery is independent of the underlying access platform and the use of Internet protocols in IMS allows for interoperability among the access platforms. IMS also leads to savings in network infrastructure, administration and management. Further, IMS allows for the migration of Circuit Switched (CS) services like voice telephony to the Packet Switched (PS) domain by using separate control and bearer functions and featuring an overlay service delivery network on top of a packet switch network infrastructure.
In IMS, media sessions may be directed to any one of multiple IMS-capable devices communicating via an IMS network. An IMS network may therefore face decisions regarding the routing of media sessions and how to signal such determinations. Additionally, multiple IMS-capable devices may be served by multiple IMS networks and the networks' functional entities, whereby the various networks may face decisions regarding the management of IMS sessions that they may seek to resolve without creating unnecessary signaling traffic.
It is therefore desirable to have a method and apparatus for IMS-capable devices to indicate routing preferences to an IMS network. It is further desirable to have a method and apparatus for IMS networks and IMS-capable devices to efficiently identify and transfer their roles.